1. Field of the Invention
The present invention relates to electronic devices, and methods for manufacturing the electronic devices. The present invention particularly relates to an electronic device, and a method for manufacturing the semiconductor device.
2. Description of the Related Art
Plastic ball grid array (PBGA) electronic devices have been proposed because thin electronic devices have been demanded. The PBGA electronic devices include substrates, electronic pieces which are mounted on the substrate and which are sealed with encapsulation resins, and solder balls serving as external terminals. The PBGA electronic devices are characterized in that the thickness of each PBGA electronic device is substantially equal to that of each substrate.
Thin PBGA packages are demanded; hence, substrates used to manufacture the PBGA packages need to be thin. Therefore, there is a problem in that wires arranged on each substrate are broken due to the warpage of the substrate before the substrate is cut into pieces.
A cause of the wire breakage is probably as follows: an external impact load is applied to the substrate in a step of cutting the substrate or during the handling of the substrate in manufacturing steps; hence, cracks are occurred in a solder resist disposed above the substrate. The solder resist is used to protect surface wires. The solder resist is made of a hard, inflexible material and is in contact with the surface wires, which are arranged in a wiring layer located closest to a surface of the substrate. The creation of the cracks generates the force to pull the surface wires in the width direction of the cracks. This causes cracks in the surface wires arranged under the solder resist. The cracks in the surface wires grow because of the mechanical stress caused by the change in the temperature of the usage environment. This will probably break the surface wires.
An increase in the thickness of the surface wires can overcome the breakage of the surface wires but cannot completely prevent the breakage thereof.
Japanese Unexamined Patent Application Publication No. 2001-77238 discloses a semiconductor device including a package in which dummy wires are arranged around wires (regular wires) relating to the operation of an element such that cracks in a substrate do not propagate to the regular wires.
The arrangement of the dummy wires around the regular wires is effective in overcoming the breakage of the regular wires. However, cracks are created in a solder resist disposed above this substrate because of the warpage of this substrate as described above. Therefore, cracks are also created in surface wires arranged under the solder resist. This leads to the breakage of these surface wires.